A potential approach is to combine an integrated population model (IPM) with a population viability analysis (PVA) to generate novel insights about population dynamics.
A comprehensive modeling framework to forecast future population dynamics while incorporating weather scenarios and vital rate variation within observed ranges that can be affected by management actions are necessary. While best management practices target vital rates that are affected by weather, focusing on a single vital rate may not be sufficient if other vital rates are secondarily limiting. Understanding the influence of severe weather is important for managing weather‐sensitive species. Increased variation in interannual weather due to climate change can exert a powerful influence on the population dynamics of a species. It will also give them access to alternative tools, particularly when predictions are required for changes in the environment that have not been experienced by a population in the past. This will help conservationists examine critically the reliability of the tools they have traditionally used to aid management decision-making. It is argued that evolutionary theory underpins Caughley's declining-population paradigm, and that it needs to become much more widely used within mainstream conservation biology. Reliable quantitative predictions about population-level responses then need to be based on an explicit consideration of the evolutionary processes operating at the individual level. Under these circumstances, vital rates and their relationship with population density will change in the future in a way that is not predictable from past patterns. Many future changes in the environment driven by management will not have been experienced by a population in the past. As a result, they can only be used to make reliable quantitative predictions about future environments when a comparable environment has been experienced by the population of interest in the past. To do this, assumptions are made about population growth or vital rates that will apply when environ- mental conditions are restored, based on either past data collected under favourable environmental conditions or estimates of these parameters when the agent of decline is removed. Statistical models of habitat use and demographic models have been used suc- cessfully to make management recommendations for declining populations. In contrast, behaviour- based models describe the evolutionary processes underlying these patterns, and derive such patterns from the strategies employed by individuals when competing for resources under a specific set of environmental conditions. Statistical models of habitat use and demo- graphic models both use descriptions of patterns in abundance and demography, in relation to a range of factors, to inform management decisions.
Each of these is described here, illustrated with a case study and evaluated critically in terms of its practical application. There are three broad classes of ecological tool used by conservationists to guide management decisions for threatened species: statistical models of habitat use, demo- graphic models and behaviour-based models. This is the declining-population paradigm identified by Caughley. Understanding the causes of population declines (past, present and future) is pivotal to designing effective practical management. The management of threatened species is an important practical way in which con- servationists can intervene in the extinction process and reduce the loss of biodiversity.
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